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Backfeeding New Service Entrance Panel While Changing Over Wiring

Backfeeding New Service Entrance Panel While Changing Over Wiring

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Old 07-07-13, 09:31 PM
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Backfeeding New Service Entrance Panel While Changing Over Wiring

Hi all,

Planning an electrical upgrade from 100A fusebox to 200A service with circuit breakers. Mainly this is in prep for a house addition, but also because the current fusebox already has a couple of double-tapped fuses.

I'm trying to minimize the downtime during the upgrade and so want to backfeed power to the new panel to provide power as I wire and switch over individual circuits.

I've read as much as I can find on this, and feel I've got a good handle on it, but wondering if someone could take a look at this and tell me if I'm missing anything?

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After the new meter base, service entrance panel and SE cables are installed, I will use 6-3 cable from a 50A fuseblock in the current box to temporarily backfeed a 50A breaker in the new panel. The main 200A breaker in the new panel is to remain OFF during the changeover.

After closing the 50A breaker to power the new panel, I will run cable for one circuit at a time, from its new breaker (open initially) to a junction point (which varies by circuit). Once cable is run, I will remove the fuse(s) for that circuit, make connections with the new cable at the junction point, then close the new circuit breaker to restore power to that circuit.

After all circuits are changed over, the local utility will de-energize the current service, then energize the new service. I will open the 50A breaker that was used for the backfeed. Then close the 200A main breaker in the new panel to restore power to all circuits.

The only circuit left at that point will be for the electric range. That's the 50A circuit I'll use temporarily, so it will be the last one to be connected, after the new service is on.

Haven't spoken with the local inspector on this yet, but will. There are a couple other questions I have for him about which circuits he will consider "upgraded" by this process, hence needing to be brought up to all current codes.

But first want to be sure I have this backfeed process straight.

Thanks for any and all help!
Keith
 
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  #2  
Old 07-07-13, 10:29 PM
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Welcome to the forums!

Your backfeedong plan sounds OK, given that you do things in the order you described.

In most jurisdictions, if you touch a circuit, it's your's all the way to meeting final by current code.
 

Last edited by Nashkat1; 07-07-13 at 11:39 PM.
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Old 07-08-13, 04:23 AM
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As a safety item, I would not allow any feeder cable from the new meter to enter the box until the last minute. Having the buss bar energized by back feed could be a problem. Make sure the old box is out of the picture when the final hook up is done.
 
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Old 07-08-13, 08:42 AM
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Haven't spoken with the local inspector on this yet, but will.
By all means, ask questions. Also, ask when the inspector wants to see the project, some times the AHJ won't allow the power company to connect the new service till after it's been inspected. I assume you have already checked to see whether a homeowner is allowed to upgrade a service, some jurisdictions do not issue permits to homeowners for this and require the work to be done by a licensed electrician. Typically, a licensed electrician will do the complete job including connecting the utility lines to the new service before he calls for a final inspection, but it would be rare to find a homeowner qualified to do it this way. The exact procedure can vary depending on the situation and the jurisdiction.
 
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Old 07-08-13, 11:29 AM
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You will need a larger (#4 copper ) Grounding Electrode Conductor between the new 200 amp Neutral bus and the existing Grounding Electrode, which may be a metallic water -servive line; do this FIRST!!! .

You may need to drive Ground-rods to "augment" the existing Grounding Electrode.
 
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Old 07-08-13, 12:51 PM
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You may need to drive Ground-rods to "augment" the existing Grounding Electrode.
The diagram in post #1 shows the existing ground rod.

That said, you will need to work out how and when you transfer that conductor to your new panel to complete the new GEC in it. A great question for your inspector.

If the existing conductor is not long enough you will have to replace it. The GEC bonding conductors must be continuous.
 
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Old 07-08-13, 02:27 PM
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While this will work, the issue is that the entire exposed buss below the main breaker will be energized while the backfeed is in place and you are cutting in the circuits as you move them over. This creates plenty of oppurtunity to contact the hot bus. Not an ideal situation. You could end up shocked or worse.
 
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Old 07-08-13, 03:42 PM
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the issue is that the entire exposed buss below the main breaker will be energized while the backfeed is in place and you are cutting in the circuits as you move them over. This creates plenty of oppurtunity to contact the hot bus.
This is true. The risk can be reduced by mounting all of the branch circuit breakers before connecting and energizing the backfeed. From the way you pointed to the exact breaker, and breaker position, that you plan to use to backfeed, it sounds like that's what you may be planning to do.
 
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Old 07-09-13, 10:32 AM
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Backfeed responses

Thank you all.

Good point on the exposed main bus. I had not thought about that yet, but I'll make sure I install all circuit breakers then remove one at a time to make connections. There will still be quite a few unused spaces on the panel (40 space panel) until I wire our house addition. Maybe I should space the breakers out (still keep the 2 legs balanced as much as possible) so there are smaller spaces between breakers rather than a large open space at the bottom?

On the grounding... The current fuse box and new panel will be on opposite ends if the house. Planning on driving two new ground rods near the new SE. Or, possibly connect grd conductor to the well casing, which is about 30 feet further away. Not sure yet if I'd need a supplemental ground rod, but it sure seems like a metal well pipe going down 100+ feet to the water table should be an excellent ground, provided I use the right clamp to connect the grd conductor.
 
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Old 07-09-13, 10:38 AM
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Also just realized, in describing the steps, I forgot that when the old service is de-energized, and before new one is energized, I will need to bond the neutral bus to the new panel. As I understand it, this is the one and only place where ground and neutral are connected, right after the service enters the house.
 
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Old 07-09-13, 12:15 PM
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Correct on the neutral and ground bond.

I would not space out the breakers. You limit yourself down the road.

Balancing a panel in a house is an act of futility.

The metal well casing will need to be bonded to the other electrodes. The only one I had to do I drilled and tapped the casing for a 1/4-20 and used a lug.
 
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Old 07-09-13, 04:38 PM
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The current fuse box and new panel will be on opposite ends if the house.
Have you contacted your power company about a new drop to the opposite end of the house. Some companies may do that, but some definitely won't and will tell you where the drop will be. After that, the electrician plans according to where the drop will be located. Just saying, check it out now before you invest a lot of time and money in your plan.
 
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Old 07-09-13, 06:46 PM
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To keep the lights on, just make the circuit the last one moved over to the new panel.

Other circuits will be fine without power for a few hours.
 
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Old 07-09-13, 09:39 PM
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Yeah, a field engineer was out last summer and discussed the location of the new service. We decided on a location that works with my plans, and is convenient to another pole from which they'll run a new underground service.
 
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